The present invention relates to a method and apparatus for automatically processing a patient""s biological fluids such as urine, blood serum, plasma, cerebrospinal fluid and the like. In particular, the present invention provides a magnetic drive system for moving liquid samples in containers held in a rack into and out of a clinical analyzer.
Various types of tests related to patient diagnosis and therapy can be performed by analysis assays of a sample of a patient""s infections, bodily fluids or abscesses for an analyte of interest. Such patient samples are typically liquids placed in sample vials, are extracted from the vials, combined with various reagents in special reaction vessels or tubes, incubated, and analyzed to aid in treatment of the patient. In a typical clinical chemical analysis, one or two assay reagents are added at separate times to a liquid sample having a known concentration, the sample-reagent combination is mixed and incubated. Interrogating measurements, turbidimetric or fluorometric or absorption readings or the like, are made to ascertain end-point or rate values from which an amount of analyte may be determined, using well-known calibration techniques.
Although various known clinical analyzers for chemical, immunochemical and biological testing of samples are available, analytical clinical technology is challenged by increasing needs for improved levels of analysis. Automated clinical analyzers improve operating efficiency by providing results more rapidly while minimizing operator or technician error. However, due to increasing demands on clinical laboratories regarding assay throughput, new assays for additional analytes, accuracy of analytical results, and low reagent consumption, there continues to be a need for improvements in the overall performance of automated clinical analyzers. In particular, the efficiency of patient sample handling continually needs to be increased, regardless of the assay to be performed.
An important contributor to maintaining a high efficiency in throughput of patient samples is the ability to quickly and securely introduce a plurality of samples to the sample testing portion of an analyzer. Patient samples are typically held in a container such as a sample cup, a primary tube, or any other suitable container and may be open at its top or closed with a stopper or lid or the like at its top. To increase handling efficiency, the containers may then be placed into a sample rack adapted to support multiple sample containers generally in an upright orientation.
The sample rack is usually placed in an input portion of the analyzer and then moved to a location where a portion of the liquid patient sample is extracted, usually by aspiration using a hollow, needle like probe from the sample container for testing in the analyzer. Afterwards, the sample rack may be moved to temporary storage area or to an output portion of the analyzer where the user can conveniently remove the sample rack from the analyzer. It is known in the art to employ magnetic conveyor mechanisms transporting a source of a magnetic field to move sample racks having a ferromagnetic element and containing open or closed sample containers along input and output lanes. Hereinafter the term ferromagnetic is intended to mean a substance having a sufficiently high magnetic permeability to be positionally affected by a changing magnetic field. Likewise, the term magnetic is intended to mean a substance that is independently capable of generating a magnetic field.
When handling sample racks supporting open sample containers, magnetic conveyor mechanisms must be designed to gradually increase the strength of the magnetic field as the magnetic conveyor mechanism approaches a sample rack, thereby providing smooth and continuous handling of a sample rack containing open sample tubes so that the possibility of spillage is minimized. Such systems require precautions to prevent abrupt movements of a sample rack so that the possibility of spillage of liquid sample from an open container is minimized and/or so that the possibility of damage, for example from re-suspension of red blood cells, to liquid sample in a closed container is minimized. U.S. Pat. No. 5,720,377 addresses this need by providing a magnetic plate positioned at the bottom surface of a sample rack and a number of belt driven magnet assemblies moving below the surface of a tray. The magnetic field generated by the magnet assemblies attract the plates disposed in the bottom surface of the sample rack and engages the plate with sufficient force such that the sample rack moves along the tray in concert with the magnet assembly as the belts move. A portion of the plate is disposed at an angle with respect to the surface of the magnet assembly such that the magnetic force provided by the magnet assembly gradually builds as the belt moves, thereby to lower the backward acceleration of the rack as the magnet assembly first approaches the sample rack. This system, however, is not operable in two opposing directions along a single lane in the tray because the angular portion is unidirectional. Such a system has disadvantages whenever an analyzer is desired to be capable of moving sample racks in two directions along a single lane, for instance when an analyzer requires only a single sample rack input/output lane to achieve needed capacity. Such disadvantages also must be overcome when modular analyzers are linked together to increase capacity and it is necessary to convert separate input and output lanes into a pair of input or output lanes.
It is therefore desirable to provide a magnetic sample transport system and sample container rack which is capable of smoothly transitioning a sample rack containing open or closed sample containers along an operating surface from a moving state to a stationary position. It is further desirable that such a magnetic sample transport system be capable of bi-directional movement of sample racks along either an input or output lane without the necessity for additional mechanisms which increase cost and design complexity and reduce reliability. It is even further desirable that such a magnetic sample transport system have a solid operating surface so that in the event of sample liquid spillage or container breakage, liquids contained in the sample containers is prevented from flowing into and harming internal portions of the analyzer and so that the operating surface may be easily cleaned. It is finally desirable that the magnetic sample transport system have no operating mechanisms above the operating surface, other than the moving sample rack, in order to eliminate moving danger points to an operator.
U.S. Pat. No. 6,206,176 discloses a magnetic drive system for moving a substrate transfer shuttle along a linear path between chambers in a semiconductor fabrication apparatus. A rack with rack magnets is secured to the shuttle, and a rotatable pinion with pinion magnets is positioned adjacent the rack so that the pinion magnets can magnetically engage the rack magnets. Rotation of the pinion causes the shuttle to move along the linear path. The magnets may be oriented with a helix angle between their primary axis and the axis of rotation of the pinion. One rack and one pinion are located on each side of the shuttle. A set of lower guide rollers supports the shuttle, and a set of upper guide rollers prevents the shuttle from lifting off the lower guide rollers.
U.S. Pat. No. 5,906,262 provides a positioning control system to control stoppage of a conveyed article with a magnetic conveyor system element on the receiving side when a conveyed article is passed between magnetic conveyor device elements in a noncontacting magnetic conveyor system. The system comprises two independently operating magnetic conveyor system elements and two drive shafts, each of which has helical magnetic poles at its surface. The carrier is equipped with magnetic poles of equal pitch to the pitch of the helical magnetic poles. When the rotary shafts rotate, the carrier moves over the guide path by a magnetic coupling action and is passed between the magnetic conveyor system elements.
U.S. Pat. No. 5,896,873 discloses an apparatus for transporting magnetic objects using a magnetic transport roller mounted to a frame for conveying a ferromagnetic carrier, and a ferromagnetic stator for rotating the transport roller. The ferromagnetic stator is integrally associated with the transport roller which has a plurality of spatially separated pole teeth. The transport roller has a magnetic core, a first bonding layer surrounding and bonded to the core, a first layer surrounding and bonded to the first bonding layer, a second bonding layer for bonding second layer to the core. The second layer is a wear and abrasion resistant material.
U.S. Pat. No. 5,871,084 discloses a conveyor system for transporting magnetic articles along an elongate path including at least one arcuate section; a chain conveyor mounted for movement through the track; at least two grids attached to the chain conveyor, a portion of each of said grids extending laterally relative to said elongate track; at least one magnet mounted on each grid for coupling by magnetic force at least one magnetically attractable article to at least one of the grids; and a connector apparatus for allowing limited movement of the article coupled by the magnet, relative to the grid, while retaining the article in engagement with the grid.
U.S. Pat. No. 5,816,385 provides for a conveying device which is capable of conveying a magnetic piece at high speed with low vibration and low noise and which makes it possible to perform a highly accurate positioning. The conveying device includes a non-magnetic rail which has a guide surface for slidably guiding a first surface of the piece and a non-magnetic conveying belt which has a conveying surface coming into contact with a second surface of the piece and which is movable along the rail. The belt is driven to rotate by a driving device. A magnet is arranged at a position opposite to the rail with the belt therebetween and generates a magnetic force having a component force which causes the second surface of the piece to be brought into close contact with the belt and a component force which causes the first surface of the piece to be brought into contact with the rail.
U.S. Pat. Nos. 5,735,387 and 5,720,377 also address a magnetic conveyor system for transporting test samples in tubes disposed in a sample rack having a magnetic or magnetically attractive region is described. The magnetic conveyor system includes a drive system, a magnet coupled to the drive system and movable in response to the drive system and a tray having a first surface adapted to receive the sample rack. The magnet is spaced a predetermined distance from the first surface of the tray such that the magnet provides a magnetic force at the surface of the tray. The magnetic force engages the magnetically attractive region of the sample rack disposed on the tray to thereby move the sample rack along the first surface of the tray in response to movement of the drive system. When the tray reaches the end of the rack it is moved onto a processing queue tray where it is available for test purposes. A barcode reader reads a bar code on each test sample as it is placed on the process queue to identify one or more tests to perform. When all samples have received the individual tests the rack exits to an output queue for disposal. When a test must be made on an immediate basis out of normal processing order a sample rack can be inserted into the process queue via a priority rack feed.
U.S. Pat. No. 5,366,697 describes a tray and conveyor for the trays for moving liquid samples in an analyzer. The tray comprises a base having a magnetic member for responding to a magnetic field, a tray frame and member for freely rotatably mounting the frame on the base, the tray frame comprising a plurality of receptacles constructed to receive either sample tubes or aspirating tips useful to aspirate sample from a tube, the receptacles including a fixed bottom support. The conveyor comprises a support, conveying members under the support comprising a plurality of magnets and members for generating a moving magnetic field with the magnets, the conveying members being mounted in a continuous loop under the support and the support being permeable to a magnetic field, one of the above-noted trays being mounted above the support on the base.
From this discussion of the art state in automated clinical analyzers, it may be seen that while considerable progress has been made toward increasing sample handling efficiency, there remains an unmet need for a system and apparatus that provides automated handling of sample racks containing open and closed sample tubes. In particular, there remains an unmet need for a system and apparatus that provides smooth and continuous handling of a sample rack containing sample tubes in either of two mutually opposing directions so that the possibility of sample damage or spillage is minimized.
The present invention provides a magnetic sample rack adapted to support one or more open test tubes, the sample rack including a ferromagnetic plate secured in a closed base cavity and a linear transport mechanism to move sample racks along a continuous operating surface. Sample racks are urged along the top of the operating surface by means of a magnetic conveyor system located beneath the solid surface. The magnetic conveyor system comprises a plurality of magnetic housings attached to a linear transport mechanism, the magnetic housings including a housing magnet slideably contained in a closed upper cavity section. The magnetic housings are sufficiently proximate the magnetic sample rack so that magnetic forces emanating from the housing magnet overcome frictional resistive forces between the sample racks and the operating surface and move the sample racks along input and output lanes defined in the operating surface. Abrupt movements of the sample racks are eliminated because the magnet slides smoothly within its housing towards the sample rack, secures the sample rack, and pulls the rack along the operating surface as the housings are moved at a steady rate by the pulley driven belt. Consequently, the sample rack smoothly transitions from a stationary position to a moving state minimizing the potential for fluid spillage from an open sample container.